Patent literature 1 discloses a fixing device shown in FIG. 7 as a fixing device for a lower-stage member to which the present invention is also directed.
In FIG. 7, two block joints (51) are mounted on a support member (52), and a fluid control unit (not shown in the drawing) which constitutes an upper-stage is mounted in a straddling manner over both joints (51). In each block joint (51), a bolt insertion hole (54) through which a joint fixing bolt (53) passes at the of mounting the block joint (51) on the support member (52) is formed. In the support member (52), a threaded hole (55) used at the time of mounting the block joint (51) on the support member (52) is formed.
The bolt insertion hole (54) formed in each block joint (51) is formed of a large-diameter portion (54a) having a diameter larger than a diameter of a bolt head portion (53a) and a small-diameter portion (54b) which is contiguously formed with the large-diameter portion (54a) byway of a stepped portion (54c) and has a diameter between the diameter of the bolt head portion (53a) and a diameter of a bolt shaft portion (53b).
A cylindrical spacer (56) which has a lower end thereof received by the support member (52) and an upper end thereof disposed in the large-diameter portion (54a) is fitted in the small-diameter portion (54b) of the bolt insertion hole (54). The spacer (56) has an inner diameter larger than a diameter of the bolt shaft portion (53b) and an outer diameter smaller than the diameter of the bolt head portion (53a). The shaft portion (53b) of the joint fixing bolt (53) is fitted into the spacer (56) and the head portion (53a) is received by an upper end surface of the spacer (56). The spacer (56) is provided for defining a fastening amount of the joint fixing bolt (53). The spacer (56) is formed such that when the joint fixing bolt (53) is made to pass through the bolt insertion hole (54) and is threaded into the threaded hole (55) formed in the support member (52), the spacer (56) is made to stretch between the bolt head portion (53a) of the joint fixing bolt (53) and the support member (52) thus stopping the further fastening of the joint fixing bolt (53).
An annular rubber washer (57) having an outer diameter approximately equal to the diameter of the head portion (53a) of the joint fixing bolt (53) is fitted on an upper end portion of the spacer (56). The rubber washer (57) is sandwiched between the head portion (53a) of the joint fixing bolt (53) and the stepped portion (54c) of the bolt insertion hole (54). A length of the rubber washer (57) in the vertical direction is set such that a compressive force is applied to the rubber washer (57) in a fastening completion state of the joint fixing bolt (53). Accordingly, both joints (51) are biased in the direction toward the support member (52) by the rubber washer (57).
In such a fixing device for a lower-stage member, the rubber washer (57) has elasticity and hence, the rubber washer (57) can be further deformed by compression. Accordingly, when upper surfaces of both joints (51) are not coplanar, one joint (51) having an upper surface lower than an upper surface of the other joint (51) can be moved upwardly.
That is, the fixing device for a lower-stage member is configured such that the respective lower-stage members (51) are fixed once and, thereafter, the desired lower-stage member (51) is moved upwardly against an elastic force of the rubber washer (57) so as to finely adjust positions of upper surfaces of a plurality of lower-stage members (51). Due to such constitution, the upper-stage members (51) can be easily mounted and, at the same time, it is possible to apply a proper amount of pressing force to all seal portions interposed between the lower-stage members (51) and the upper-stage members so that sealing property can be ensured. Patent literature 1 exemplifies the rubber washer (57) having a rectangular cross section as the elastic member.